Granular materials such as salt, sand, magnesium chloride, calcium chloride, cinders, and/or other deicers are spread on roadways during the winter to help melt snow and ice. An automated spreader device is commonly employed to perform this task. Such spreader devices are used in conjunction with large trucks as well as smaller vehicles such as pickup trucks. A spreader device used in conjunction with a pickup truck is typically mounted on the tailgate and/or tow hitch of the pickup truck. One known spreader device employs a hopper for holding the granular material and an auger for urging the granular material toward an opening for discharging the granular material from the hopper. The discharged granular material falls onto a finned rotating spinner plate that propels the granular material in a radial pattern. This action distributes the granular material over a wide area of the road surface.
Granular material tends to leak from the outlet of the known spreader device, especially when the vehicle travels over bumps in the road. Even though the blade of the auger partially obstructs the outlet of the hopper when the auger is not rotating, granular material still may slip past the auger blade and fall out of the outlet. Consequently, when the vehicle is driven between spreading jobs, the granular material undesirably leaks from the hopper outlet even in the absence of auger rotation.